- RB Cronje and IM Ratlapane
- Agricultural Research Council - Institute for Tropical and Subtropical Crops, Private Bag X 11208, Nelspruit 1200, RSA
- 2017
Autumn flush control with ethephon is an important orchard management practice to ensure good flowering and cropping. Flush growth just before and during the flower induction period can lead to reduced crops, as these shoots will not mature in time to produce flowers. Due to new cultivars being planted in the South African litchi industry, flush control has to be re-evaluated for each cultivar due to their different sensitivities to ethephon. ‘Early Delight’, for example, a new early cultivar that is increasingly planted, appears to be more sensitive to ethephon. In order to determine the optimum concentrations as well as to register ethephon for use on ‘Early Delight’, trials were carried out in 2014 and 2016 with concentrations between O and 1000 ppm. Applications were done during April as spot sprays as per current industry practice for ‘Mauritius’ and ‘McLean’s Red’. The results showed that 500 ppm with the addition of a wetter is most successful in removing autumn flush and increasing yield in ‘Early Delight’. Lower concentrations than 500 ppm are less effective and higher concentrations may lead to phytotoxicity.
Summary:
- Autumn flush control using ethephon is vital for good flowering and yield in litchi orchards, as flush growth close to flower induction reduces crop yield by producing immature shoots that do not flower.
- The study focused on the ‘Early Delight’ cultivar, which is more sensitive to ethephon compared to traditional cultivars Mauritius and McLean’s Red. Trials in 2014 and 2016 tested ethephon concentrations between 0 to 1000 ppm applied as spot sprays in April during new soft flush growth.
- Results showed that 500 ppm ethephon combined with a wetter (Sanawett) was most effective at flushing control and increasing yield. Lower concentrations (350 ppm) were less effective, while higher concentrations (750 and 1000 ppm) caused phytotoxicity symptoms like leaf drop, especially under stress conditions.
- Flush control was assessed by measuring percentage flush removal, flowering percentage, and yield. Trees treated with 500 ppm showed higher flowering and yield compared to untreated and lower concentration treatments.
- The conclusion is that 500 ppm ethephon with a wetter is the recommended effective concentration for flush control in ‘Early Delight’ to maximize flowering and yield while minimizing phytotoxicity risks